Physicists in the US have made a chip-sized refrigerator that can cool objects much bigger than itself to millikelvin temperatures. The device relies on the quantum mechanical tunnelling of electrons between a metal and superconductor and could find applications in a variety of cryogenic sensors in the semiconductor industry and astronomy (A M Clark et al. 2005 Appl. Phys. Lett. 86 173508).

Chip-scale refrigerator Many next-generation scientific instruments will rely on sensors cooled to temperatures near 100 millikelvin (mK). However, present-day solid-state refrigerators cannot go below about 1 K. Moreover, the cooling techniques that can reach 100 mK are complicated and expensive.